U.S. patent number 6,919,171 [Application Number 10/744,923] was granted by the patent office on 2005-07-19 for silver-(carboxylate-azine toner) particles for photothermographic and thermographic imaging.
This patent grant is currently assigned to Eastman Kodak Company. Invention is credited to Thomas Blanton, John W. Boettcher, David A. Dickinson, Peter J. Ghyzel, Roger L. Klaus, Mark Lelental, Joe E. Maskasky, Victor P. Scaccia, James L. Wakley.
United States Patent |
6,919,171 |
Lelental , et al. |
July 19, 2005 |
Silver-(carboxylate-azine toner) particles for photothermographic
and thermographic imaging
Abstract
The present disclosure relates to aqueous dispersions of silver
(carboxylate-azine toner) particles wherein the azine content of
the particles is from about 0.01 to 10% by weight relative to
silver carboxylate. The carboxylates are typically silver salts of
long chain fatty acids and the azine toners are the compounds that
function as development accelerators and toning agents such as
phthalazine. These silver (carboxylate-azine) particles can be used
to formulate imaging forming compositions that are useful in
aqueous thermographic or photothermographic imaging elements.
Inventors: |
Lelental; Mark (Rochester,
NY), Ghyzel; Peter J. (Rochester, NY), Boettcher; John
W. (Webster, NY), Wakley; James L. (Brockport, NY),
Dickinson; David A. (Brockport, NY), Maskasky; Joe E.
(Rochester, NY), Klaus; Roger L. (Victor, NY), Scaccia;
Victor P. (Rochester, NY), Blanton; Thomas (Rochester,
NY) |
Assignee: |
Eastman Kodak Company
(Rochester, NY)
|
Family
ID: |
30000071 |
Appl.
No.: |
10/744,923 |
Filed: |
December 23, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
|
200426 |
Jul 22, 2002 |
6692906 |
|
|
|
Current U.S.
Class: |
430/617; 430/600;
430/613; 430/620; 430/631; 430/640; 430/964; 430/965 |
Current CPC
Class: |
G03C
1/49845 (20130101); G03C 1/005 (20130101); G03C
1/49809 (20130101); Y10S 430/165 (20130101); Y10S
430/166 (20130101) |
Current International
Class: |
G03C
1/498 (20060101); G03C 1/005 (20060101); G03C
001/35 (); G03C 001/494 () |
Field of
Search: |
;430/620,619,631,964,965,600,613,617,640 ;503/201,207 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Chea; Thorl
Attorney, Agent or Firm: Hawley; J. Jeffrey
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATIONS
This is a divisional of application Ser. No. 10/200,426, filed Jul.
22, 2002 now U.S. Pat. No. 6,692,906.
Claims
What is claimed is:
1. An aqueous dispersion of silver (carboxylate-azine toner)
particles having incorporated therein an azine toner compound
silver carboxylate wherein the azine content of the particles is
from about 0.01 to 10% by weight relative to silver
carboxylate.
2. The aqueous dispersion of silver (carboxylate-azine toner)
particle according to claim 1 wherein said particles further
include carboxylic acid in an amount from about 0.01 to 20% by
weight relative to the silver carboxylate.
3. The aqueous dispersion of silver (carboxylate-azine toner)
particle according to claim 1 wherein said particles are
nanoparticulate.
4. The aqueous dispersion of silver (carboxylate-azine toner)
particle according to claim 1 wherein said particles are stabilized
by having on their surface a surface modifier that is a nonionic
oligomeric surfactant based on vinyl polymers with an amido
function.
5. The aqueous dispersion of silver (carboxylate-azine toner)
particle according to claim 1 wherein said silver salt is a salt of
a long chain fatty acid containing 8 to 30 carbon atoms.
6. The aqueous dispersion of silver (carboxylate-azine toner)
particle according to claim 1 wherein said silver carboxylate is
silver behenate.
7. The aqueous dispersion of silver (carboxylate-azine toner)
particle according to claim 1 wherein said azine toner is
phthalazine.
8. A thermographic element comprising a support having thereon a
layer containing the dispersion according to claim 1.
9. A thermographic element comprising a support having thereon a
layer containing the dispersion according to claim 4.
10. An aqueous oxidation-reduction imaging forming composition
comprising (i) a dispersion silver (carboxylate-azine toner)
particles containing an azine toner compound and silver carboxylate
wherein the azine content of the particles is from about 0.01 to
10% by weight relative to silver carboxylate, and said particles
having on the surface thereof a surface modifier which is a
nonionic oligomeric surfactant based on vinyl polymer with an amido
function and (ii) an organic reducing agent.
11. The aqueous oxidation-reduction imaging forming composition
according to claim 10 wherein said particles further include
carboxylic acid in an amount from about 0.01 to 20% by weight
relative to the silver carboxylate.
12. The aqueous oxidation-reduction imaging forming composition
according to claim 10 wherein said particles are
nanoparticulate.
13. The aqueous oxidation-reduction imaging forming composition
according to claim 10 wherein said particles are stabilized by
having on their surface a surface modifier that is a nonionic
oligomeric surfactant based on vinyl polymers with an amido
function.
14. The aqueous oxidation-reduction imaging forming composition
according to claim 10 wherein said silver salt is a salt of a long
chain fatty acid containing 8 to 30 carbon atoms.
15. The aqueous oxidation-reduction imaging forming composition
according to claim 10 wherein said silver carboxylate is silver
behenate.
16. The aqueous oxidation-reduction imaging forming composition
according to claim 10 wherein said azine toner is phthalazine.
17. A thermographic element comprising a support having thereon a
layer containing the the aqueous oxidation-reduction imaging
forming composition according to claim 10.
18. A thermographic element comprising a support having coated
thereon: an oxidation-reduction imaging forming composition
comprising (i) a dispersion of silver (carboxylate-azine toner)
particles containing an azine toner compound and silver carboxylate
wherein the azine content of the particles is from about 0.01 to
10% by weight relative to silver carboxylate, and (ii) an organic
reducing agent, and (iii) a hydrophilic polymer binder.
19. The thermographic element of claim 18 further comprising on the
surface of said silver (carboxylate-azine toner) particles, a
surface modifier that is a nonionic oligomeric surfactant based on
a vinyl polymer with an amido function.
20. The thermographic element of claim 18 wherein the
oxidation-reduction imaging formulation comprises a
polyhydroxybenzene.
21. The thermographic element of claim 18 further comprising a
toner/development accelerator.
22. The thermographic element of claim 18 wherein the hydrophilic
polymer binder is gelatin or a gelatin derivative.
Description
FIELD OF THE INVENTION
This invention relates to aqueous dispersions of silver
(carboxylate-azine toner) particles. The carboxylates are typically
silver salts of long chain fatty acids and the azine toners are the
compounds that function as development accelerators and toning
agents. These silver (carboxylate-azine) particles are used to
formulate imaging forming compositions that are useful in aqueous
photothermographic or thermographic imaging elements. In another
aspect, the invention relates to a coprecipitation method for
producing the particles.
DESCRIPTION RELATIVE TO THE PRIOR ART
Thermographic and photothermographic materials and imaging elements
are well known in the photographic art. These materials are also
known as heat developable photographic materials. Thermographic
materials can form an image by the imagewise application of heat.
Photothermographic materials include a light sensitive material,
for example a silver halide. After imagewise exposure
photothermographic materials are heated to moderately elevated
temperatures to produce a developed image in the absence of
separate processing solutions or baths.
An example of a known photothermographic silver halide material
comprises (a) a hydrophilic photosensitive silver halide emulsion
containing a gelatino peptizer with (b) an organic solvent mixture,
(c) a hydrophobic binder and (d) an oxidation-reduction
image-forming composition. The oxidation-reduction imaging forming
composition typically comprises (i) a silver carboxylate that is
usually a silver salt of a long-chain fatty acid, such as silver
behenate or silver stearate, in combination with (ii) an organic
reducing agent, such as a phenolic reducing agent. It has been
desirable to have hydrophilic photosensitive silver halide emulsion
containing a gelatino peptizer in such a photothermographic
material because of the higher photosensitivity of the silver
halide emulsion and the ease of control in preparation of the
emulsion based on conventional aqueous silver halide gelatino
emulsion technology.
A problem has been encountered in preparing these
photothermographic silver halide materials. This problem involves
the mixing of a hydrophilic photosensitive silver halide emulsion
containing a gelatino peptizer with an oxidation-reduction imaging
forming composition. The imaging forming composition contains
hydrophobic components including a hydrophobic binder, such as
poly(vinyl butyral), and a silver salt of a long-chain fatty acid,
such as a silver salt of behenic acid. Typically, when the
hydrophilic photosensitive silver halide emulsion is mixed with the
hydrophobic imaging forming materials and then coated on a suitable
support to produce a photothermographic element, the resulting
element produces a less than desired degree of photosensitivity,
contrast and maximum density upon exposure and heat processing.
This problem has been encountered in photothermographic silver
halide materials, as described in, for example, U.S. Pat. No.
3,666,477 of Goffe, issued May 30, 1972. Goffe proposed addition of
alkylene oxide polymers and a mercaptotetrazole derivative to the
photothermographic material to help provide increased
photosensitivity. In addition, a variety of organic solvents have
been proposed in order to help prepare a photothermographic silver
halide composition containing the described image-forming
components. The organic solvents that have been proposed include
isopropanol, acetone, toluene, methanol, 2-methoxyethanol,
chlorinated solvents, acetone-toluene mixtures and certain
non-aqueous polar organic solvents. The described individual
solvents, such as isopropanol, have not provided the desired
improved properties. There has been a continuing need to provide
improved relative speed, contrast and image tone with desired
maximum image density.
It is known to provide toners in thermographic and
photothermographic compositions to increase chemical reactivity of
the development chemistry and to improve the tone of the developed
image. The compositions described herein are typically used to
produce elements that are useful in x-ray imaging. For diagnostic
purposes, doctors prefer neutral images on blue tinted support. The
images should have very low minimum density and very high maximum
density for optimum diagnostic use. The use of toner compounds can
help accomplish these objectives.
A variety of toner compositions are known. For example, in EP
0803764 A1 filed 16 Apr. 1997, there is described a thermographic
composition having a succinimide toner incorporated in the
composition (See Example 1).
The materials and imaging elements described herein can be used as
output media and can be exposed using a laser printer, typically
from a digitized x-ray image. Laser printers of interest typically
expose the elements to infrared laser radiation, for example in the
800 nm range. Since silver halide is not inherently sensitive to
infrared radiation, it must be spectrally sensitized to this
wavelength range in order to be effectively exposed.
Recent developments have focused on providing imaging compositions,
for example photothermographic compositions, that are aqueous
based. Such compositions, compared to organic solvent-based
compositions, have numerous coating advantages. For example,
expensive organic solvent recovery systems are not necessary in the
coating process.
In commonly assigned U.S. Pat. No. 5,350,669 to Witcomb et al,
issued Sep. 27, 1994, there are disclosed compositions comprising
silver, carboxylate and azine as the primary non-photosensitive,
reducible silver source for a photothermographic element. These
compounds contain relatively large amounts of the expensive azine
component. The minimum amount of azine disclosed by Witcomb et al
is about 14% by weight relative to silver carboxylate. (This
assumes the minimum mass associated with the azine structure and a
maximum for the carboxylate within the ranges specified.)
We have found that the presence of azine toner compounds
significantly impacts the ability to spectrally sensitize a
photosensitive silver halide emulsion in an aqueous environment.
The inability to maintain sufficient spectral sensitization causes
it to be difficult to maintain an adequate maximum density in the
processed elements. Succinimide toner does not desensitize infrared
sensitized silver halide.
SUMMARY OF THE INVENTION
In one aspect of the invention, there is provided an aqueous
dispersion of silver-carboxylate particles having incorporated
therein an azine toner compound. The azine content of the silver
(carboxylate-azine toner) particles is from about 0.01 to 10% by
weight relative to silver carboxylate, preferably about 0.05 to 5%.
Other species can also be present, for example about 0.01 to 20% by
weight relative to the silver carboxylate can be carboxylic acid,
preferably 5 to 15% and about 0.01 to 2% by weight relative to the
silver carboxylate can be alkali metal carboxylate salt (for
example sodium or potassium carboxylate etc.) preferably 0.5 to
1.5%.
As will be seen in the comparative examples below, these silver
(carboxylate-azine toner) particles substantially avoid the
desensitization of spectrally sensitized silver halide. While not
wishing to be bound by any particular theory, we believe that the
desensitization by azine toner compounds in prior compositions can
be attributed to the desorption of the spectral sensitizing dye
from the surface of the silver halide grains. This in turn may be
caused by the presence of the "free" azine toner compound. In the
present invention, the azine toner is incorporated into the
carboxylate particles and is therefore not "free" to desensitize
adjacent silver halide grains. These particles provide the desired
silver development kinetics, image density and image tone.
As noted, a characteristic of the present invention is that the
silver-carboxylate particles have an azine toner compound
incorporated into the structure of the particles. Another aspect of
the invention is that the azine is present in a small amount. We
have found that this small amount provides the desired development
acceleration and image toning. Compositions using such small
amounts are cheaper and less likely to produce interference with
the spectral sensitizer than are compositions using larger amounts
of azine toner. Further, high levels of azine, even if complexed
with silver carboxylate, results in higher d-min than desired and
less than desired raw stock keeping characteristics. Being
incorporated into the particle means that the azine toner is not
free but rather is part of the particle in the same sense, for
example, as would be a dopant. One of the characteristics of such a
particle is that the x-ray diffraction pattern resembles the
pattern obtained from the silver-carboxylate. In contrast, if
silver carboxylate particles are simply mixed with silver-azine
toner particles, a second novel crystallographic phase is observed
in the x-ray diffraction pattern of the mixture. These particles
will be referred to as "silver(carboxylate-azine toner)
particles".
In preferred embodiments of the invention, the silver
(carboxylate-azine toner) particles incorporated into the aqueous
composition exhibit nanoparticulate morphology. It is particularly
preferred that at least a portion of the non-photosensitive source
of reducible silver ions be provided in the form of an aqueous
nanoparticulate dispersion of silver (carboxylate-azine toner)
particles having the desired content of azine. By nanoparticulate,
we mean that the silver (carboxylate-azine toner) particles in such
dispersions preferably have a weight average particle size of less
than 1000 nm when measured by any useful technique such as
sedimentation field flow fractionation, photon correlation
spectroscopy, or disk centrifugation. In one particular method of
measuring particle size the silver carboxylate and silver
(carboxylate-azine toner) particle size and it's distribution is
determined using a Horiba LA-920, He--Ne, laser particle size
analyzer. This analyzer measures the particle size distribution by
angular light scattering technique. Obtaining such small silver
(carboxylate-azine toner) particles can be achieved using a variety
of techniques described in the copending applications identified in
the following paragraphs, but generally they are achieved using
high speed milling using a device such as those manufactured by
Morehouse-Cowles and Hochmeyer. The details for such milling are
well known in the art.
In another aspect of the invention, there is provided an aqueous
oxidation-reduction imaging forming composition comprising (i) a
dispersion silver (carboxylate-azine toner) particles wherein the
azine content of the particles is from about 0.01 to 10% by weight
relative to silver carboxylate said particles having on the surface
of the particles a surface modifier which is a nonionic oligomeric
surfactant based on vinyl polymer with an amido function and (ii)
an organic reducing agent. This composition can be coated on a
support to provide a useful thermographic element.
In another aspect of the invention, there is provided an aqueous
photothermographic composition comprising a) an infrared spectrally
sensitized photosensitive silver halide emulsion containing a
gelatino peptizer and b) an oxidation-reduction imaging forming
composition comprising (i) a dispersion of silver
(carboxylate-azine) particles wherein the azine content of the
particles is from about 0.01 to 10% by weight relative to silver
carboxylate said particles having on the surface of the particles a
surface modifier which is a nonionic oligomeric surfactant based on
a vinyl polymer with an amido function and (ii) an organic reducing
agent. The described photothermographic composition can be coated
on a support to provide a useful photothermographic element.
DETAILED DESCRIPTION OF THE INVENTION
This invention solves, or greatly minimizes the prior art
desensitization problems referred to above. A process is provided
that produces an aqueous silver (carboxylate-azine) particle
dispersion. Furthermore, the preferred process of this invention
provides aqueous colloidal dispersions containing small particles
with narrow particle size distribution. The imaging elements
comprising silver (carboxylate-azine) particles exhibit greatly
improved photographic properties and superior raw stock keeping
characteristics in comparison to the elements formulated by adding
"free" azine toner during the preparation of the coating melt. The
images produced using photothermographic elements of this invention
exhibit low turbidity, high optical density and neutral tone. The
potential losses of spectral sensitivity in the extrinsic region of
the silver halide photo response e.g. IR, caused by silver
halide-sensitizing dye--"free" azine toner interactions, are
minimized by the incorporation of the toner in the form of a
bound-azine toner compound within the silver (carboxylate-azine)
particles. The preferably nanoparticulate, aqueous,
silver-carboxylate, silver-azine toner particle dispersions are
easy to filter and display excellent shelf life. These dispersions
have been successfully incorporated with the other necessary
ingredients into an aqueous photothermographic imaging element and
successfully exposed and thermally processed using a laser printer
and thermal processor.
The particles in such dispersions can be stabilized by having on
their surface a surface modifier so the silver salt can more
readily be incorporated into aqueous-based photothermographic
formulations. Useful surface modifiers include, but are not limited
to, nonionic oligomeric surfactants based on vinyl polymers having
an amino function, such as polymers prepared from acrylamide,
methacrylamide, or derivatives thereof, as described in copending
and commonly assigned POLYACRYLAMIDE SURFACE MODIFIERS FOR SILVER
CARBOXYLATE NANOPARTICLES, Lelental, Pitt, Dickinson, Wakley and
Ghyzel, Published application US 20010031436 A1 Aug. 18, 2001. A
particularly useful surface modifier is dodecylthiopolyacrylamide
that can be prepared as described in the noted copending
application using the teaching provided by Pavia et al.,
Makromoleculare Chemie, 193(9), 1992, pp. 2505-17.
Other useful surface modifiers are phosphoric acid esters, such as
mixtures of mono- and diesters of orthophosphoric acid and
hydroxy-terminated, oxyethylated long-chain alcohols or
oxyethylated alkyl phenols as described for example in PHOSPHORIC
ACID ESTER SURFACE MODIFIERS FOR SILVER CARBOXYLATE NANOPARTICLES,
Lelental, Dickinson, Wakley, Orem and Ghyzel, Published application
US 20010029001 A1 Aug. 18, 2001. Particularly useful phosphoric
acid esters are commercially available from several manufacturers
under the trademarks or tradenames EMPHOSTM (Witco Corp.), RHODAFAC
(Rhone-Poulenc), T-MULZ.RTM. (Hacros Organics), and TRYFAC (Henkel
Corp./Emery Group).
Such dispersions contain smaller particles and narrower particle
size distributions than dispersions that lack such surface
modifiers. Particularly useful nanoparticulate dispersions are
those comprising silver carboxylates such as silver salts of long
chain fatty acids having from 8 to 30 carbon atoms, including, but
not limited to, silver behenate, silver caprate, silver
hydroxystearate, silver myristate, silver palmitate, and mixtures
thereof. Silver behenate nanoparticulate dispersions are most
preferred. These nanoparticulate dispersions can be used in
combination with the conventional silver salts described above,
including but not limited to, silver benzotriazole, silver
imidazole, and silver benzoate. In another aspect of the invention,
there is provided an aqueous oxidation-reduction imaging forming
composition comprising (i) a dispersion of silver
(carboxylate-azine toner) particles as described having on the
surface of the particles a surface modifier which is a nonionic
oligomeric surfactant based on vinyl polymer with an amido function
and (ii) an organic reducing agent.
In the case of controlled coprecipitation of metal salts or
complexes such as water insoluble silver (carboxylate-azine)
particles, the surface modifiers offer higher degree of particle
size reduction, an improved colloidal stability of the dispersed
system, higher chemical reactivity and lower low-shear viscosity.
The nanoparticulate silver (carboxylate-azine) particles increase
the reactivity of the silver metal-forming oxidation-reduction
photothermographic development chemistry and hence, a lower
temperature and (or) shorter development time is required to
generate final silver image and to maximize image discrimination.
Furthermore, the use of nanoparticulate silver(carboxylate-azine
toner) particles in the film microstructure provides for a
significant reduction of the film turbidity generally attributed to
the particle size controlled light scattering improved image
density and neutral image tone.
The present invention relates to a dispersion of silver
(carboxylate-azine toner) particles. Particularly preferred
silver-carboxylates are silver salts of long chain fatty acids such
as, for example, silver stearate, silver behenate, silver caprate,
silver hydroxystearate, silver myristate and silver palmitate. The
preferred azine toner compounds are phthalazine and substituted
phthalazine.
X-ray diffraction patterns show the described silver
(carboxylate-azine toner) is different from a simple mixture of
silver-carboxylate and silver-azine toner. Silver
(behenate-phthalazine) has an x-ray diffraction pattern that is
very similar to silver-behenate while a mixture of silver-behenate
and silver phthalazine exhibits an addition phase.
The use of nonsilver (carboxylate-azine toner) toners/development
accelerators or derivatives thereof which improve the image density
and tone, is highly desirable, to the element. Toners may be
present in amounts of from 0.01 to 20 percent by weight of the
emulsion layer, preferably from 0.1 to 10 percent by weight. In
addition to the toner that is present in the silver
(carboxylate-azine toner) particles, additional toner may be
present. These other toners can be present to provide enhanced
chemical reactivity and to adjust tone as desired. For sensitized
materials, toners should be chosen that do not desensitize the
spectrally sensitized silver halide. Toners are well known
materials in the photothermographic art as shown in U.S. Pat. Nos.
3,080,254; 3,847,612 and 4,123,282. Examples of useful toners
include phthalimide and N-hydroxyphthalimide; cyclic imides such as
succinimide, pyrazoline-5-ones, and a quinazolinone,
1-phenylurazole, 3-phenyl-2-pyrazoline-5-one, quinazoline and
2,4-thiazo lidinedione; naphthalimides such as
N-hydroxy-1,8-naphthalimide; cobalt complexes such as cobaltic
hexaminetrifluoroacetate; mercaptans as illustrated by
3-mercapto-1,2,4-triazole, 2,4-dimercaptopyrimidine,
3-mercapto-4,5-diphenyl-1,2,4-triazole and
2,5-dimercapto-1,3,4-thiadiazole;
N-(aminomethyl)aryldicarboximides,
e.g.(N,N-dimethylaminomethyl)phthalimide, and
N-(dimethylaminomethyl)naphthalene-2,3-dicarboximide, and a
combination of blocked pyrazoles, isothiuronium derivatives and
certain photobleach agents, e.g., a combination of
N,N'-hexamethylene-bis(1-carbamoyl-3,5-dimethylpyrazole),
1,8-(3,6-diazaoctane)bis(isothiuronium)trifluoroacetate and
2-(tribromomethylsulfonyl benzothiazole); and merocyanine dyes such
as
3-ethyl-5-[(3-ethyl-2-benzothiazolinylidene)-1-methylethylidene]-2-thio-2,
4-oazolidinedione; phthalazinone, phthalazinone derivatives or
metal salts or these derivatives such as
4-(1-naphthyl)phthalazinone, 6-chlorophthalazinone,
5,7-dimethoxyphthalazinone, and 2,3-dihydro-1,4-phthalazinedione; a
combination of phthalazine plus one or more phthalic acid
derivatives, e.g., phthalic acid, 4-methylphthalic acid,
4-nitrophthalic acid, and tetrachlorophthalic arthydride;
quinazolinediones, benzoxazine or naphthoxazine derivatives;
rhodium complexes .quadrature.g., ammonium peroxydisulfate and
hydrogen peroxide; benzoxazine-2,4-diones such as
1,3-benzoxazine-2,4-dione, 8-methyl-1,3-benzoxazine-2,4-dione, and
6-nitro-1,3-benzoxazine-2,4-dione; pyrimidines and asymtriazines,
e.g., 2,4-dihydroxypyrimidine, 2-hydroxy-4-aminopyrimidine, and
azauracil, and tetrazapentalene derivatives, e.g.,
3,6-dimercapto-1,4-diphenyl-1H,4H-2,3a,5,6a-tetrazapentalene, and
1,4-di(o-chlorophenyl)-3,6-dimercapto-1H,4H-2,3a,5,6a-tetrazapentalene.
The azine in the silver (carboxylate-azine) particles of the
invention is from the class of organic compounds known as azines
having the general structure R1R2C.dbd.N--N.dbd.CR3R4. The azine
structure preferably completes a six membered ring to form
pyridazine or two six membered fused rings to form phthalazine and
cinnoline. The rings can be substituted with for example, alkyl,
substituted alkyl, hydroxy, alkoxy, and carboxy and carboxy-ester
groups. Suitable azine compounds are: phthalazine, pyridazine,
cinnoline, benzo(c) cinnoline, Examples of preferred substituted
diazine compounds are: 1(2H)-phthalazinone, substituted
1(2H)-phthalazinones, 2,3-dihydro-1,4-phthalazinedione, substituted
2,3-dihydro-1,4-phthalazinediones and the like. In a particularly
preferred embodiment the azine compound is phthalazine or a
substituted phthalazine.
Other compounds can also be incorporated in silver-carboxylate
particles. Silver-thiolates incorporated into the particles reduce
the photographic fog associated with the compositions. The
incorporation of silver thiolates is not our invention but is the
invention of our coworkers, Ghyzel, Lelental, Dickinson, Pitt and
Wear and is the subject of copending, commonly assigned U.S. Ser.
No. 09/764,677 filed on the same date as this application. The
preferred thiols are linear alkyl thiolates having alkyl chains of
2 to 24 carbons with the most preferred thiolates have alkyl chains
of 6 to 18 carbons. Examples include but are not limited to silver
1-hexanethiolate, silver 1-dodecanethiolate, and silver
1-octadecanethiolate. The preferred level of silver-thiolate is
from 0.1 to 1.2% by weight based on the weight of the
silver-carboxylate. The thiols can be incorporated along with
carboxylate and azine toner to produce a silver(carboxylate-azine
toner-thiol) particle. Alternatively, particles of
silver(carboxylate-thiol) can be prepared and used in combination
with silver(carboxylate-azine toner) particles.
A number of surface modifiers can be used to facilitate the
formation of nanoparticulate silver (carboxylate-azine) particles.
Particular examples are disclosed in the following copending,
commonly assigned applications: POLYACRYLAMIDE SURFACE MODIFIERS
FOR SILVER CARBOXYLATE NANOPARTICLES, Lelental, Pitt, Dickinson,
Wakley and Ghyzel, cited above; and PHOSPHORIC ACID ESTER SURFACE
MODIFIERS FOR SILVER CARBOXYLATE NANOPARTICLES, Lelental,
Dickinson, Wakley, Orem and Ghyzelalso cited above.
The preferred surface modifiers are polyacrylamide modifiers that
are broadly defined by either of the following formulas:
##STR1##
The number of hydrophobic groups (R or R.sup.1 & R.sup.2)
depends on the linking group L. The hydrophobic group or groups
comprise a saturated or unsaturated alkyl, aryl-alkyl or alkyl-aryl
group where the alkyl parts can be straight or branched. Typically
the groups R or R.sup.1 & R.sup.2 comprise 8-21 carbon atoms.
The linking group L is linked to the hydrophobic groups by a simple
chemical link and to the oligomeric part T by a thio link
(--S--).
Typical linking groups for materials with one hydrophobic group are
illustrated as follows: ##STR2##
Typical linking groups for materials with two hydrophobic groups
are illustrated as follows: ##STR3##
The oligomeric group T is based on the oligomerisation of vinyl
monomers with an amido function, the vinyl part providing the route
to oligomerisation and the amido part providing a nonionic polar
group to constitute the hydrophilic functional group (after
oligomerisation). The oligomeric group T can be made up from a
single monomer source or a mixture of monomers provided the
resulting oligomeric chain is sufficiently hydrophilic to render
the resulting surface active material soluble or dispersible in
water. Typical monomers used to create the oligomeric chain T are
based on acrylamide, methacrylamide, derivatives of acrylamide,
derivatives of methacrylamide and 2-vinylpyrollidone, though the
latter is less favored due to adverse photographic effects
sometimes found with polyvinyl pyrrolidone (PVP).
These monomers can be represented by two general formulas:
##STR4##
X is typically H or CH.sub.3, which leads to an acrylamide or
methacrylamide based monomer respectively.
Y and Z' are typically H, CH.sub.3, C.sub.2 H.sub.5, C(CH.sub.2
OH).sub.3 where X and Y can be different or the same.
The described oligomeric surfactant based on vinyl polymer with an
amido function can be made by methods that are known in the art or
are simple modifications of known methods. An illustrative
preparation is provided below.
In another aspect, the present invention provides a process for
making aqueous silver (carboxylate-azine) particle dispersions.
Nanoparticulate silver (carboxylate-azine toner) particle
dispersions can be prepared by a precipitation process commonly
used for the precipitation of photographic silver halide emulsions.
Into a conventional reaction vessel for silver precipitation
equipped efficient stirring mechanism is introduced a surface
modifier. Typically the surface modifier initially introduced into
the reaction vessel is at least about 5 percent, preferably 10 to
30 percent, by weight based on total weight of the surface modifier
present in the nanoparticulate-silver (carboxylate-toner)
dispersion the conclusion of grain precipitation. Since surface
modifier can be removed from the reaction vessel by ultrafiltration
during silver (carboxylate-azine) particle dispersion
precipitation, as taught by Mignot U.S. Pat. No. 4,334,012, it is
appreciated that the volume of surface modifier initially present
in the reaction vessel can equal or even exceed the volume of the
silver-carboxylate, silver-azine toner particles present in the
reaction vessel at the conclusion of grain precipitation. The
surface modifier initially introduced into the reaction vessel is
preferably aqueous solution or an aqueous dispersion of surface
modifier, optionally containing other ingredients, such as one or
more antifoggant and/or various dopants, more specifically
described below. Where a surface modifier is initially present, it
is preferably employed in a concentration of at least 5 percent,
most preferably at least 10 percent, of the total surface modifier
present at the completion of silver (carboxylate-azine) particle
dispersion precipitation. Additional surface modifier can be added
to the reaction vessel with the water-soluble silver salts and can
also be introduced through a separate jet.
During precipitation silver carboxylate salts and azine toner
compound(s) are added to the reaction vessel by techniques well
known in the precipitation of photographic silver halide grains.
The carboxylate salts are typically introduced as aqueous salt
solutions, such as aqueous solutions of one or more soluble
ammonium, alkali metal (e.g., sodium or potassium), or alkaline
earth metal (e.g., magnesium or calcium) carboxylate salts. The
water-soluble or water dispersible toner compound(s) and the silver
salt are at least initially introduced into the reaction vessel
separately from the carboxylate salt.
With the introduction of silver salt into the reaction vessel the
nucleation stage of silver (carboxylate-azine) grain(s) formation
is initiated. A population of grain nuclei is formed which is
capable of serving as precipitation sites for silver
(carboxylate-azine) particles or grains as the introduction of
silver and (or) carboxylic acid salts and (or) azine toner
compound(s) continues. The precipitation of silver
(carboxylate-azine) particles onto existing grain nuclei
constitutes the growth stage of nanoparticulate grain
formation.
The silver, azine toner compound(s) and carboxylic salt or
carboxylic acid grains are preferably very fine e.g., less than 1.0
micron in mean diameter. The concentrations and rates of silver,
toner compound(s) and carboxylic acid salt introductions can take
any convenient conventional form. The silver, azine toner
compound(s) and carboxylic acid salts are preferably introduced in
concentrations of from 0.1 to 5 moles per liter, although broader
conventional concentration ranges, such as from 0.01 mole per liter
to saturation, for example, are contemplated. Specifically
preferred coprecipitation techniques are those which achieve
shortened precipitation times by increasing the rate of silver,
toner compound(s) and carboxylic acid salt introduction during the
run. The rate of silver, toner compound(s) and or carboxylic acid
salt introduction can be increased either by increasing the rate at
which the silver and or carboxylic acid salts are introduced or by
increasing the concentrations of the silver, toner compound(s) and
carboxylic acid salts within the solution.
The individual silver and (or) toner compound(s) carboxylic acid
salts can be added to the reaction vessel through surface or
subsurface delivery tubes by gravity feed or by delivery apparatus
for maintaining control of the rate of delivery and the pH, and/or
pAg of the reaction vessel contents, as illustrated by Culhane et
al. U.S. Pat. No. 3,821,002, Oliver U.S. Pat. No. 3,031,304 and
Claes et al., Photographische Korrespondenz, Band 102, Nov. 10,
1967, p. 162. In order to obtain rapid distribution of the
reactants within the reaction vessel, specially constructed mixing
devices can be employed, as illustrated by Audran U.S. Pat. No.
2,996,287, McCrossen et al. U.S. Pat. No. 3,342,605, Frame et al.
U.S. Pat. No. 3,415,650, Porter et al. U.S. Pat. No. 3,785,777,
Finnicum et al. U.S. Pat. No. 4,147,551, Verhille et al. U.S. Pat.
No. 4,171,224, Calamur U.K. Patent Application No. 2,022,431A,
Saito et al. German OLS Nos. 2,555,364 and 2,556,885, and Research
Disclosure, Volume 166, February 1978, Item 16662.
In forming the silver (carboxylate-azine) particle dispersions a
surface modifier is initially contained in the reaction vessel. In
a preferred form the surface modifier is comprised of an aqueous
solution. Surface modifier concentrations of from 0.1 to about 30
percent by weight, based on the total weight of dispersion
components in the reaction vessel, can be employed. It is common
practice to maintain the concentration of the surface modifier in
the reaction vessel in the range of below about 15 percent, based
on the total weight, prior to and during silver carboxylate-silver
toner compound combination formation. It is contemplated that the
silver (carboxylate-azine) particle dispersion as initially formed
will contain from about 1 to 150 grams of surface modifier per mole
of silver carboxylate preferably about 25 to 75 grams of surface
modifier per mole of silver. Additional surface modifier can be
added later to bring the concentration up to as high as 200 grams
per mole of silver.
Vehicles (which include both binders and peptizers) can be
employed. Preferred peptizers are hydrophilic colloids, which can
be employed alone or in combination with hydrophobic materials.
Suitable hydrophilic materials include substances such as proteins,
protein derivatives, cellulose derivatives e.g., cellulose esters,
gelatin e.g., alkali-treated gelatin (cattle bone or hide gelatin)
or acid-treated gelatin (pigskin gelatin), gelatin derivatives
e.g., acetylated gelatin, phthalated gelatin and the like,
polysaccharides such as dextran, gum arabic, zein, casein, pectin,
collagen derivatives, agaragar, arrowroot, albumin and the like as
described in Yutzy et al. U.S. Pat. Nos. 2,614,928 and '929, Lowe
et al., U.S. Pat. Nos. 2,691,582, 2,614,930, '931, 2,327,808 and
2,448,534, Gates et al. U.S. Pat. Nos. 2,787,545 and 2,956,880,
Himmelmann et al. U.S. Pat. No. 3,061,436, Farrell et al. U.S. Pat.
No. 2,816,027, Ryan U.S. Pat. Nos. 3,132,945, 3,138,461 and
3,186,846, Dersch et al. U.K. Pat. No. 1,167,159 and U.S. Pat. Nos.
2,960,405 and 3,436,220, Geary U.S. Pat. No. 3,486,896, Gazzard
U.K. Pat. No. 793,549, Gates et al. U.S. Pat. Nos. 2,992,213,
3,157,506, 3,184,312 and 3,539,353, Miller et al. U.S. Pat. No.
3,227,571, Boyer et al. U.S. Pat. No. 3,532,502, Malan U.S. Pat.
No. 3,551,151, Lohmer et al. U.S. Pat. No. 4,018,609, Luciani et
al. U.K. Pat. No. 1,186,790, Hori et al. U.K. Pat. No. 1,489,080
and Belgian Pat. No. 856,631, U.K. Pat. No. 1,490,644, U.K. Pat.
No. 1,483,551, Arase et al. U.K. Pat. No. 1,459,906, Salo U.S. Pat.
Nos. 2,110,491 and 2,311,086, Fallesen U.S. Pat. No. 2,343,650,
Yutzy U.S. Pat. No. 2,322,085, Lowe U.S. Pat. No. 2,563,791, Talbot
et al. U.S. Pat. No. 2,725,293, Hilborn U.S. Pat. No. 2,748,022,
DePauw et al. U.S. Pat. No 2,956,883, Ritchie U.K. Pat. No. 2,095,
DeStubner U.S. Pat. No. 1,752,069, Sheppard et al. U.S. Pat. No.
2,127,573, Lierg U.S. Pat. No. 2,256,720, Gaspar U.S. Pat. No.
2,361,936, Farmer U.K. Pat. No. 15,727, Stevens U.K. Pat. No.
1,062,116 and Yamamoto et al. U.S. Pat. No. 3,923,517.
Photosensitive silver halide grains made using water dispersible
cationic starch to control fog can also be used. The use of
cationic starch in photothermographic elements is not our invention
but is the invention of our coworkers, Maskasky, Dickinson and
Lelental and is described in copending, commonly assigned U.S. Ser.
No. 09/703,050 filed 31 Oct. 2000.
Other materials commonly employed in combination with hydrophilic
colloid peptizers as vehicles (including vehicle extenders--e.g.,
materials in the form of lattices) include synthetic polymeric
peptizers, carriers and/or binders such as poly(vinyl lactams),
acrylamide polymers, polyvinyl alcohol and its derivatives,
polyvinyl acetals, polymers of alkyl and sulfoalkyl acrylates and
methacrylates, hydrolyzed polyvinyl acetates, polyamides, polyvinyl
pyridine, acrylic acid polymers, maleic anhydride copolymers,
polyalkylene oxides, methacrylamide copolymers, polyvinyl
oxazolidinones, maleic acid copolymers, vinylamine copolymers,
methacrylic acid copolymers, acryloyloxyalkylsulfonic acid
copolymers, sulfoalkylacrylamide copolymers, polyalkyleneimine
copolymers, polyamines, N,N-dialkylaminoalkyl acrylates, vinyl
imidazole copolymers, vinyl sulfide copolymers, halogenated styrene
polymers, amineacrylamide polymers, polypeptides and the like as
described in Hollister et al. U.S. Pat. Nos. 3,679,425, 3,706,564
and 3,813,251, Lowe U.S. Pat. Nos. 2,253,078, 2,276,322, '323,
2,281,703, 2,311,058 and 2,414,207, Lowe et al. U.S. Pat. Nos.
2,484,456, 2,541,474 and 2,632,704, Perry et al. U.S. Pat. No.
3,425,836, Smith et al. U.S. Pat. Nos. 3,415,653 and 3,615,624,
Smith U.S. Pat. No. 3,488,708, Whiteley et al. U.S. Pat. Nos.
3,392,025 and 3,511,818, Fitzgerald U.S. Pat. Nos. 3,681,079,
3,721,565, 3,852,073, 3,861,918 and 3,925,083, Fitzgerald et al.
U.S. Pat. No. 3,879,205, Nottorf U.S. Pat. No. 3,142,568, Houck et
al. U.S. Pat. Nos. 3,062,674 and 3,220,844, Dann et al. U.S. Pat.
No. 2,882,161, Schupp U.S. Pat. No. 2,579,016, Weaver U.S. Pat. No.
2,829,053, Alles et al. U.S. Pat. No. 2,698,240, Priest et al. U.S.
Pat. No. 3,003,879, Merrill et al. U.S. Pat. No. 3,419,397, Stonham
U.S. Pat. No. 3,284,207, Lohmer et al. U.S. Pat. No. 3,167,430,
Williams U.S. Pat. Nos. 2,957,767, Dawson et al. U.S. Pat. No.
2,893,867, Smith et al. U.S. Pat. Nos. 2,860,986 and 2,904,539,
Ponticello et al. U.S. Pat. Nos. 3,929,482 and 3,860,428,
Ponticello U.S. Pat. No. 3,939,130, Dykstra U.S. Pat. No. 3,411,911
and Dykstra et al. Canadian Pat. No. 774,054, Ream et al. U.S. Pat.
No. 3,287,289, Smith U.K. Pat. No. 1,466,600, Stevens U.K. Pat. No.
1,062,116, Fordyce U.S. Pat. No. 2,211,323, Martinez U.S. Pat. No.
2,284,877, Watkins U.S. Pat. No. 2,420,455, Jones U.S. Pat. No.
2,533,166, Bolton U.S. Pat. No. 2,495,918, Graves U.S. Pat. No.
2,289,775, Yackel U.S. Pat. No. 2,565,418, Unruh et al. U.S. Pat.
Nos. 2,865,893 and 2,875,059, Rees et al. U.S. Pat. No. 3,536,491,
Broadhead et al. U.K. Pat. No. 1,348,815, Taylor et al. U.S. Pat.
No. 3,479,186, Merrill et al. U.S. Pat. No. 3,520,857, Bacon et al.
U.S. Pat. No. 3,690,888, Bowman U.S. Pat. No. 3,748,143, Dickinson
et al. U.K. Pat. Nos. 808,227 and '228, Wood U.K. Pat. No. 822,192
and Iguchi et al. U.K. Pat. No. 1,398,055. These additional
materials need not be present in the reaction vessel during
nanoparticulate silver (carboxylate-azine) dispersion
precipitation, but rather are conventionally added to the
dispersion prior to coating. The vehicle materials, including
particularly the hydrophilic colloids, as well as the hydrophobic
materials useful in combination therewith can be employed not only
in the emulsion layers of the photographic elements of this
invention, but also in other layers, such as overcoat layers,
interlayers and layers positioned beneath the emulsion layers. The
silver (carboxylate-azine) particle dispersions are preferably free
of soluble salts. The soluble salts can be removed by decantation,
filtration, and/or chill setting and leaching, as illustrated by
Craft U.S. Pat. No. 2,316,845 and McFall et al U.S. Pat. No.
3,396,027; by coagulation washing, as illustrated by Hewitson et
al. U.S. Pat. No. 2,618,556, Yutzy et al. U.S. Pat. No. 2,614,928,
Yackel U.S. Pat. No. 2,565,418, Hart et al. U.S. Pat. No.
3,241,969, Waller et al. U.S. Pat. No. 2,489,341, Klinger U.K. Pat.
No. 1,305,409 and Dersch et al. U.K. Pat. No. 1,167,159; by
centrifugation and decantation of a coagulated dispersion as
illustrated by Murray U.S. Pat. No. 2,463,794, Ujihara et al. U.S.
Pat. No. 3,707,378, Audran U.S. Pat. No. 2,996,287 and Timson U.S.
Pat. No. 3,498,454; by employing hydrocyclones alone or in
combination with centrifuges, as illustrated by U.K. Pat. No.
1,336,692, Claes U.K. Pat. No. 1,356,573 and Ushomirskii et al.
Soviet Chemical Industry, Vol. 6, No. 3, 1974, pp. 181-185; by
diafiltration with a semipermeable membrane, as illustrated by
Research Disclosure, Vol. 102, October 1972, Item 10208, Hagemaier
et al. Research Disclosure, Vol. 131, March 1975, Item 13122,
Bonnet Research Disclosure, Vol. 135, July 1975, Item 13577, Berg
et al. German OLS No. 2,436,461, Bolton U.S. Pat. No. 2,495,918,
and Mignot U.S. Pat. No. 4,334,012, cited above, or by employing an
ion exchange resin, as illustrated by Maley U.S. Pat. No. 3,782,953
and Noble U.S. Pat. No. 2,827,428.
In one aspect, there is provided an aqueous oxidation-reduction
imaging forming composition comprising (i) a dispersion of
silver-carboxylate and silver (carboxylate-azine) particles wherein
the azine content of the particles is from about 0.01 to 10% by
weight relative to silver carboxylate said particles having on the
surface of the particles a surface modifier which is a nonionic
oligomeric surfactant based on vinyl polymer with an amido function
and (ii) an organic reducing agent. Such a composition is useful,
for example, in a thermographic element. An image can be formed in
such an element by imagewise heating. Imagewise heating can be
accomplished using an array of heating elements as the element is
passed through a machine similar to a facsimile machine.
In another aspect, the compositions of the invention can be used in
photothermographic elements wherein a photosensitive silver halide
is present. Exposure of the silver halide produces a latent image
that is then developed by a composition of the invention including
silver (carboxylate-azine) particles. An aqueous photothermographic
composition according to the invention can be prepared by very
thoroughly mixing (I) a hydrophilic photosensitive silver halide
emulsion with (II) (a) a hydrophilic binder and (b) an
oxidation-reduction image-forming composition comprising (i) an
aqueous dispersion of silver-carboxylate and silver
(carboxylate-azine toner) particles wherein the azine content of
the particles is from about 0.01 to 10% by weight relative to
silver carboxylate with (ii) an organic reducing agent in water. A
photothermographic can be prepared by coating the resulting
photothermographic composition on a suitable support.
The aqueous photothermographic materials can comprise a
photosensitive silver halide. The photosensitive silver halide is
in the form of a hydrophilic photosensitive silver halide emulsion
containing a gelatino peptizer. The photosensitive silver halide is
especially useful due to its high degree of photosensitivity
compared to other photosensitive components.
Spectral sensitization is the addition of compounds to silver
halide grains which absorb radiation at wavelengths other than
those to which silver halide is naturally sensitive (i.e., only
within the UV to blue) or which absorb radiation more efficiently
than silver halide (even within those natural regions of spectral
sensitivity). It is generally recognized that spectral sensitizers
extend the responses of photosensitive silver halide to longer
wavelengths and can accomplish spectral sensitization the UV,
visible or infrared regions of the electromagnetic spectrum. These
compounds, after absorption of the radiation, transfer energy to
the silver halide grains to cause the necessary local photoinduced
reduction of silver salt to silver metal. The compounds are usually
dyes, and the best method of spectrally sensitizing silver halide
grains causes or allows the dyes to align themselves on the surface
of the silver halide grain, particularly in a stacked, almost
crystalline pattern on the surface of the individual grains.
Many cyanine and related dyes are well known for their ability to
impart spectral sensitivity to a gelatino silver halide element.
The wavelength of peak sensitivity is a function of the dye's
wavelength of peak light absorbance. While many such dyes provide
some spectral sensitization in photothermographic formulations, the
dye sensitization is often very inefficient and it is not possible
to translate the performance of a dye in gelatino silver halide
elements to photothermographic elements. The emulsion making
procedures and chemical environment of photothermographic elements
are very harsh compared to those of gelatino silver halide
elements. The presence of large surface areas of fatty acids and
fatty acid salts as well as other components of photothermographic
formulations restricts the surface deposition of sensitizing dyes
onto silver halide surfaces and may remove sensitizing dye from the
surface of the silver halide grains. The large variations in
pressure, temperature, pH and solvency encountered in the
preparation of photothermographic formulation aggravate the
problem. Thus sensitizing dyes that perform well in gelatino silver
halide elements are often inefficient in photo-thermographic
formulations. In general, it has been found that merocyanine dyes
are superior to cyanine dyes in photothermographic formulations as
disclosed, for example, in British Patent No 1,325,312 and U.S.
Pat. No. 3,719,495. Recently, certain cyanine dyes have been
disclosed as spectral sensitizers for use in photothermographic
elements. For example, U.S. Pat. Nos. 5,441,866 and 5,541,054
describe photothermographic elements spectrally sensitized with
benzothiazole heptamethine dyes substituted with various groups,
including alkoxy and thioalkyl. Although spectral sensitizing dyes
for photothermographic elements are now known which absorb
through-out the visible and near-infrared regions (i.e., 400-850
nm) photothermographic emulsions which provide higher photographic
speeds and which have improved shelf-life stability, sensitivity,
contrast and low Dmin are still needed for photothermography. U.S.
Pat. No. 4,207,108 (Hiller) describes improved speed in
photothermographic materials by addition of a photographic speed
increasing concentration of a certain non-dye, thione speed
increasing addendum (including compounds with cyclic thiocarbonyl
[>COS] groups within the cyclic structure). No decomposition of
the cyclic thione compounds is reported. U.S. Pat. No. 5,541,055
(Ooi et al.) describes photothermographic elements that comprise
both a cyanine dye and a colorless cyclic carbonyl compound.
Rhodanine, hydantoin, barbituric acid, or derivatives thereof (all
shown to be monocyclic in columns 4-6) are particularly preferred
as the colorless cyclic carbonyl compound. The recent commercial
availability of relatively high powered semiconductor light
sources, and particularly laser diodes which emit in the red and
near-infrared region of the electromagnetic spectrum, as sources
for out-put of electronically stored image data onto photosensitive
film or paper is becoming increasingly wide spread. This has led to
a need for high quality imaging articles, which are sensitive at
these wavelengths, and has created a need for more highly sensitive
photothermographic elements to match such exposure sources both in
wavelength and intensity.
To get the speed of the photothermographic elements up to maximum
levels and further enhance sensitivity, it is often desirable to
use supersensitizers. Any supersensitizer can be used which
increases the sensitivity. For example, preferred infrared
supersensitizers are described in U.S. patent application Ser. No.
08/091,000 (filed Jul. 13, 1993) and include heteroaromatic
mercapto compounds or heteroaromatic disulfide compounds of the
formulae: Ar--S--M and Ar--S--S--Ar,
wherein M represents a hydrogen atom or an alkali metal atom. In
the above noted supersensitizers, Ar represents a heteroaromatic
ring or fused heteroaromatic ring containing one or more of
nitrogen, sulfur, oxygen, selenium or tellurium atoms. Preferably,
the heteroaromatic ring comprises benzimidazole, naphthimidazole,
benzothiazole, naphthothiazole, benzoxazole, naphthoxazole,
benzoselenazole, benzotellurazole, imidazole, oxazole, pyrazole,
triazole, thiazole, thiadiazole, tetrazole, triazine, pyrimidine,
pyridazine, pyrazine, pyridine, purine, quinoline or quinazolinone.
However, other heteroaromatic rings are envisioned under the
breadth of this invention. The heteroaromatic ring may also carry
substituents with examples of preferred substituents being selected
from the group consisting of halogen (e.g., Br and Cl), hydroxy,
amino, carboxy, alkyl (e.g., of 1 or more carbon atoms, preferably
1 to 4 carbon atoms) and alkoxy (e.g., of 1 or more carbon atoms,
preferably of 1 to 4 carbon atoms. Most preferred supersensitizers
are 2-mercaptobenzimidazole, 2-mercapto-5-methylbenzimidazole
(MMBI), 2-mercaptobenzothiazole, and 2-mercaptobenzoxazole (MBO).
The supersensitizers are used in general amount of at least 0.001
moles of sensitizer per mole of silver in the emulsion layer.
Usually the range is between 0.001 and 1.0 moles of the compound
per mole of silver and preferably between 0.01 and 0.3 moles of
compound per mole of silver.
A typical concentration of hydrophilic photosensitive silver halide
emulsion containing a gelatino peptizer and the imaging forming
composition according to the invention is within the range of about
0.02 to about 1.0 mole of photosensitive silver halide per mole of
the described silver (carboxylate-azine) particles in the
photothermographic material. Other photosensitive materials can be
useful in combination with the described photosensitive silver
halide if desired. Preferred photosensitive silver halides are
silver chloride, silver bromoiodide, silver bromide, silver
chlorobromoiodide or mixtures thereof. For purposes of the
invention, silver iodide is also considered to be a photosensitive
silver halide. A range of grain size and grain morphology of
photosensitive silver halide from very coarse grain to very fine
grain and from 3D to tabular silver halide is useful. Tabular grain
photosensitive silver halide is useful, as described in, for
example, U.S. Pat. No. 4,435,499. Very fine grain silver halide is
typically preferred.
The hydrophilic photosensitive silver halide emulsion containing a
gelatino peptizer can be prepared by any of the procedures known in
the photographic art which involve the preparation of photographic
silver halide gelatino emulsion. Useful procedures and forms of
photosensitive silver halide gelatino emulsions for purposes of the
invention are described in, for example, the Product Licensing
Index, Volume 92, December 1971, Publication 9232 on page 107,
published by Industrial Opportunities Limited, Homewell, Havant
Hampshire, P09 1EF, UK. The photographic silver halide, as
described, can be washed or unwashed, can be chemically sensitized
using chemical sensitization procedures. Materials known in the
photographic art can be protected against the production of fog and
stabilized against loss of sensitivity during keeping as described
in the mentioned Product Licensing Index publication.
A hydrophilic photosensitive silver halide emulsion containing a
gelatino peptizer that contains a low concentration of gelatin is
often very useful. The concentration of gelatin that is very useful
is typically within the range of about 9 to about 40 grams per mole
of silver. (The term "hydrophilic" is intended herein to mean that
the photosensitive silver halide emulsion containing a gelatino
peptizer is compatible with an aqueous solvent.)
The gelatino peptizer that is useful with the photosensitive silver
halide emulsion can comprise a variety of gelatino peptizers known
in the photographic art. The gelatino peptizer can be, for example,
phthalated gelatin or non-phthalated gelatin. Other gelatino
peptizers that are useful include acid or base hydrolyzed gelatins.
A non-phthalated gelatin peptizer is especially useful with the
described photosensitive silver halide emulsion.
The photosensitive silver halide emulsion can contain a range of
concentration of the gelatino peptizer. Typically, the
concentration of the gelatino peptizer is within the range of about
5 grams to about 60 grams of gelatino peptizer, such as gelatin,
per mole of silver in the silver halide emulsion. This is described
herein as a low-gel silver halide emulsion. An especially useful
concentration of gelatino peptizer is within the range of about 10
to about 25 grams of gelatino peptizer per mole of silver in the
silver halide emulsion. The optimum concentration of the gelatino
peptizer will depend upon such factors as the particular
photosensitive silver halide, the desired image, the particular
components of the photothermographic composition, coating
conditions and the like.
The temperature of the reaction vessel within which the silver
halide emulsion is prepared is typically maintained within a
temperature range of about 35.degree. C. to about 75.degree. C.
during the composition preparation. The temperature range and
duration of the preparation can be altered to produce the desired
emulsion grain size and desired composition properties. The silver
halide emulsion can be prepared by means of emulsion preparation
techniques and apparatus known in the photographic art.
A variety of hydrophilic binders are useful in the described
photothermographic materials. The binders that are useful include
various colloids alone or in combination as vehicles and/or binding
agents. The hydrophilic binders which are suitable include
transparent or translucent materials and include both naturally
occurring substances, such as proteins, gelatin, gelatin
derivatives, cellulose derivatives, polysaccharides, such as
dextrin, gum arabic and the like: and synthetic polymeric
substances such as water-soluble polyvinyl compounds like polyvinyl
alcohol, poly (vinyl pyrrolidone), acrylamide polymers and the
like. Other synthetic polymeric compounds, which can be employed,
include dispersed vinyl compounds such as latex form and
particularly those that increase dimensional stability of
photographic materials. A range of concentration of hydrophilic
binder can be useful in the photothermographic silver halide
materials according to the invention. Typically, the concentration
of hydrophilic binder in a photothermographic silver halide
composition according to the invention is within the range of about
0.5 to about 10 g/m2. An optimum concentration of the described
binder can vary depending upon such factors as the particular
binder, other components of the photothermographic material,
coating conditions, desired image, processing temperature and
conditions and the like.
If desired, a portion of the photographic silver halide in the
photothermographic composition according to the invention can be
prepared in situ in the photothermographic material. The
photothermographic composition, for example, can contain a portion
of the photographic silver halide that is prepared in or on one or
more of the other components of the described photothermographic
material rather than prepared separate from the described
components and then admixed with them. Such a method of preparing
silver halide in situ is described in, for example, U.S. Pat. No.
3,457,075 of Morgan et al., issued Jul. 22, 1969.
The described photothermographic composition comprises an
oxidation-reduction image-forming combination containing silver
(carboxylate-azine) particles, with a suitable reducing agent. The
oxidation-reduction reaction resulting from this combination upon
heating is believed to be catalyzed by the latent image silver from
the photosensitive silver halide produced upon imagewise exposure
of the photothermographic material followed by overall heating of
the photothermographic material. The exact mechanism of image
formation is not fully understood.
A variety of organic reducing agents are useful in the described
photothermographic silver halide materials. These are typically
silver halide developing agents that produce the desired
oxidation-reduction image-forming reaction upon exposure and
heating of the described photothermographic silver halide material.
Examples of useful reducing agents include: polyhydroxybenzenes,
such as hydroquinone and alkyl substituted hydroquinones; catechols
and pyrogallol; phenylenediamine developing agents; aminophenol
developing agents; ascorbic acid developing agents, such as
ascorbic acid and ascorbic acid ketals and other ascorbic acid
derivatives; hydroxylamine developing agents; 3-pyrazolidone
developing agents such as 1-phenyl-3-pyrazolidone and
4-methyl-4-hydroxymethyl-1-phenyl-3-pyrazolidone; hydroxytetronic
acid and hydroxytetronamide developing agents; reductone developing
agents; bis-naphthol reducing agents; sulfonamidophenol reducing
agents: hindered phenol reducing agents and the like. Combinations
of organic reducing agents can be useful in the described
photothermographic silver halide materials. Sulfonamidophenol
developing agents, such as described in Belgian Pat. No. 802,519
issued Jan. 18, 1974 can be especially useful in the
photothermographic silver halide composition.
A range of concentration of the organic reducing agent can be
useful in the described photothermographic silver halide materials.
The concentration of organic reducing agent is typically within the
range of about 0.5 g/m2 to about 5 g/m2, such as within the range
of about 1.0 to about 3.0 g/m2. The optimum concentration of
organic reducing agent will depend upon such factors as the
particular carboxylate, e.g. long-chain fatty acid, the desired
image, processing conditions, the particular solvent mixture,
coating conditions and the like.
The order of addition of the described components for preparing the
photothermographic composition before coating the composition onto
a suitable support is important to obtain optimum photographic
speed, contrast and maximum density.
Various mixing devices are useful for preparing the described
compositions. However, the mixing device should be one that
provides very thorough mixing. Mixing devices that are useful are
commercially available colloid mill mixers and dispersator mixers
known in the photographic art.
Photothermographic materials according to the invention can contain
other addenda that are useful in imaging. Suitable addenda in the
described photothermographic materials include development
modifiers that function as speed-increasing compounds, hardeners,
antistatic layers, plasticizers and lubricants, coating aids,
brighteners, spectral sensitizing dyes, antifogants, charge control
agents, absorbing and filter dyes, matting agents and the like.
The specific addenda depend on the exact nature of the imaging
element. The present invention is useful for forming laser output
media useful for reproducing x-ray images; it is useful for forming
microfilm elements and it is useful to form graphic arts elements.
Each of these applications has well known features requiring
specialized addenda known in the respective arts for these
elements.
As noted, the present invention provides silver (carboxylate-azine)
particles. An important advantage of these compositions is that
they can be coated from an aqueous environment. Several current
elements of this type are currently coated from organic solvents.
The described materials can be used to convert these products into
aqueous coated products, particularly where the particles are
nanoparticulate. In this process, some of the components that are
typically found in these elements might not be as soluble in water
as desired. These components also can be made into nanoparticulate
dispersions using the same or compatible surface modifiers as are
described.
It is useful in certain cases to include a stabilizer in the
described photothermographic material. This can help in
stabilization of a developed image. Combinations of stabilizers can
be useful if desired. Typical stabilizers or stabilizer precursors
include certain halogen compounds, such as tetrabromobutane and
2-(tribromomethyl)sulfonyl, benzothiazole, which provide improved
postprocessing stability and azothioethers and blocked azoline
thione stabilizer precursors.
A photothermographic element according to the invention can have a
transparent protective layer comprising a film forming binder,
preferable a hydrophilic film forming binder. Such binders include,
for example, crosslinked polyvinyl alcohol, gelatin, poly (silicic
acid), and the like. Particularly preferred are binders comprising
poly (silicic acid) alone or in combination with a water-soluble
hydroxyl-containing monomer or polymer as described in the U.S.
Pat. No. 4,828,971.
The term "protective layer" is used to mean a transparent, image
insensitive layer that can be an overcoat layer, that is a layer
that overlies the image sensitive layer(s). The protective layer
can also be a backing layer, that is, a layer that is on the
opposite side of the support from the image sensitive layer(s). The
imaging element can contain an adhesive interlayer or adhesion
promoting interlayer between the protective layer and the
underlying layer(s). The protective layer is not necessarily the
outermost layer of the imaging element.
The protective layer can contain an electrically conductive layer
having a surface resistivity of less than 5.times.10.sup.11
ohms/square. Such electrically conductive overcoat layers are
described, for example, in U.S. Pat. No. 5,547,821.
A photothermographic imaging element can include at least one
transparent protective layer containing matte particles. Either
organic or inorganic matte particles can be used. Examples of
organic matte particles are beads of polymers such as polymeric
esters of acrylic and methacrylic acid, e.g., poly
(methylmethacrylate), styrene polymers and copolymers, and the
like. Examples of inorganic matte particles are glass, silicon
dioxide, titanium dioxide, magnesium oxide, aluminum oxide, barium
sulfate, calcium carbonate, and the like. Matte particles and the
way they are used are further described in U.S. Pat. Nos.
3,411,907, 3,754,924, 4,855,219, 5,279,934, 5,288,598, 5,378,577,
5,563,226 and 5,750,328.
A wide variety of materials can be used to prepare the protective
backing layer that is compatible with the requirements of
photothermographic elements. The protective layer should be
transparent and should not adversely affect sensitometric
characteristics of the photothermographic element such as minimum
density, maximum density and photographic speed. Useful protective
layers include those comprised of poly (silicic acid) and a
water-soluble hydroxyl containing monomer or polymer that is
compatible with poly (silicic acid) as described in U.S. Pat. Nos.
4,741,992 and 4,828,971, the entire disclosures of which are
incorporated herein by reference. A combination of poly (silicic
acid) and poly (vinyl alcohol) is particularly useful. Other useful
protective layers include those formed from polymethylmethacrylate,
acrylamide polymers, cellulose acetate, crosslinked polyvinyl
alcohol, terpolymers of acrylonitrile, vinylidene chloride, and
2-(methacryloyloxy)ethyl-trimethylammonium methosulfate,
crosslinked gelatin, polyesters and polyurethanes.
Particularly preferred protective layers are described in
above-mentioned U.S. Pat. Nos. 5,310,640 and 5,547,821.
The photothermographic elements can comprise a variety of supports
that can tolerate the processing temperatures useful in developing
an image. Typical supports include cellulose ester, poly(vinyl
acetal), poly(ethylene terephthalate), polycarbonate and polyester
film supports. Related film and resinous support materials, as well
as paper, glass, metal and the like supports that can withstand the
described processing temperatures are also useful. Typically a
flexible support is most useful.
Coating procedures known in the photographic art can coat the
photothermographic compositions on a suitable support. Useful
methods including dip coating, air-knife coating, bead coating
using hoppers, curtains coating or extrusion coating using hoppers.
If desired, two or more layers can be coated simultaneously.
The described silver halide and oxidation-reduction image-forming
combination can be in any suitable location in the
photothermographic element which produces the desired image. In
some cases it can be desirable to include certain percentages of
the described reducing agent, the silver salt oxidizing agent
and/or other addenda in a protective layer or overcoat layer over
the layer containing the other components of the element as
described. The components, however, must be in a location that
enables their desired interaction upon processing.
It is necessary that the photosensitive silver halide, as described
and other components of the imaging combination are "in reactive
association" with each other in order to produce the desired image.
The term "in reactive association," as employed herein, is intended
to mean that the photosensitive silver halide and the image-forming
combination are in a location with respect to each other, which
enables the desired processing and produces a useful image.
A useful embodiment of the invention is a photothermographic silver
halide composition capable of being coated on a support. The
composition comprises (a) an aqueous photosensitive silver halide
emulsion containing a gelatin peptizer with (b) a hydrophilic
polymeric binder consisting essentially of a gelatin and (c) an
oxidation-reduction image-forming combination comprising (i) a
silver carboxylate and the described silver (carboxylate-azine
toner) particles and a surface modifier as described (ii) an
organic reducing agent consisting essentially of a hindered phenol.
This composition can be coated on a suitable support to produce a
photothermographic element. Another embodiment is a method of
preparing a photothermographic element comprising coating the
resulting composition onto a suitable support to produce a
photothermographic element as desired.
Elements can be imaged using a variety of methods. The elements can
be imaged using any suitable source of infrared radiation to which
the photothermographic material is sensitive. Typically, a
photothermographic material is exposed imagewise with an infrared
light source, such as a laser or a light emitting diode (LED) to
produce a developable latent image.
A visible image can be developed in the photothermographic material
within a short time, such as within several seconds, merely by
heating the photothermographic material to moderately elevated
temperatures. For example, the exposed photothermographic material
can be heated to a temperature within the range of about
100.degree. C. to about 200.degree. C., such as a temperature
within the range of about 110.degree. C. to about 140.degree. C.
Heating is carried out until a desired image is developed,
typically within about 2 to about 60 seconds, such as 8 to 30
seconds. Selection of an optimum processing time and temperature
will depend upon such factors as the desired image, particular
components of the photothermographic element, the particular latent
image and the like.
The necessary heating of the described photothermographic material
to develop the desired image can be accomplished in a variety of
ways. Heating can be accomplished using a simple hot plate, iron,
roller, infrared heater, hot air or the like.
Processing is typically carried out under ambient conditions of
pressure and humidity. Pressures and humidity outside normal
atmospheric conditions can be useful if desired; however, normal
atmospheric conditions are preferred.
EXAMPLES
Example 1
Procedure for Precipitation of Nanoparticulate Colloidal Dispersion
Comprising Silver(Behenate-Phthalazine Toner) Particles
Starting Materials
Demineralized Water Nominally 90% Behenic Acid (Unichema)
recrystallized from isopropanol to purify ML-41Surfactant
(described in Published application US20010031436 A1 Aug. 18, 2001)
12.77% (w/w) aqueous silver nitrate 10.81% (w/w) aqueous potassium
hydroxide 1-dodecanethiol phthalazine
Precipitation Procedure
A 20 gallon reactor was charged with 31.5 kg of water, 135 g ML-41,
4.05 g 1-dodecanethiol and 925.6 g of behenic acid. The contents
were stirred at 150 RPM with a retreat curve stirrer and heated to
70.degree. C. Once the mixture reached 70.degree. C., 1243.6 g of
10.81% aqueous potassium hydroxide and 26.2 g of phthalazine were
added to the reactor. The mixture was heated to 80.degree. C. and
held there for 30 minutes. The mixture was then cooled to
70.degree. C. When the reactor reached 70.degree. C., 3125 g of
12.77% aqueous silver nitrate were fed to the reactor in 5 minutes.
After the addition, the nanoparticulate silver
(behenate-phthalazine toner) compound combination was held at the
reaction temperature for 30 minutes. It was then cooled to room
temperature and washed by ultrafiltration. A silver
(behenate-phthalazine toner) compound combination dispersion with a
median particle size of 160 nm was obtained.
Example 2
Aqueous Photothermographic Imaging Element Formulated Using
Nanoparticulate Ag (Beh-Phthalazine Toner) Dispersion Made Using
Controlled Precipitation
The photosensitive emulsion layer was prepared by combining at
40.degree. C., 55 grams of 35% aqueous solution of gelatin peptizer
(cattle bone, alkali treated, deionized gelatin) with 109.8 grams
of water and 128.4 grams of an aqueous nanoparticulate
silver(behenate-phthalazine toner) particle dispersion prepared as
described in Example 1. To this mixture was added 2.8 grams of a 25
g/l aqueous solution of AF-1, 0.96 grams of solid particle
dispersion of AF-2 (described below), 2.72 grams of succinimide
toner and 3.97 grams of 50 g/l aqueous solution of sodium iodide.
This mixture was combined with 35.0 grams of a solid particle
dispersion of developer Dev-1 (described below) and was stirred
overnight. A primitive iodobromide cubic emulsion, Br 97% I 3%, 48
nanometer in edge length and containing 20 g gelatin per mole
silver was melted at 40 C and was spectrally sensitized at 40 C by
combining 9.44 grams of emulsion 0.775 kg/mol Ag with 6.07 grams of
a 3 g/l aqueous solution of D-1 (described below) followed by
addition of 0.99 grams of a 7 g/l methanolic solution of D-2
(described below). This mixture was held for 10 minutes and chill
set. Prior to coating at 40.degree. C. the silver behenate
containing mixture described above was combined with 14.8 grams of
spectrally sensitized emulsion with good stirring. To this mixture
was added 3.89 grams of a solution made by adding 100 g/ of
4-methyl phthalic acid and 76 g/l of sodium bicarbonate.
The solid particle dispersion of the developer Dev-1 had been
prepared by milling a 20% solution of Dev-1 with 0.8% SDS in water.
The solid particle dispersion of AF-2 had been prepared by milling
a 20% solution of AF-2 with 2.0% of Triton.RTM. X-200 (Rohm and
Haas, Philadelphia Pa.) in water.
A thermally processable imaging element was prepared by coating a
gelatin subbed poly(ethylene terephthalate) support, having a
thickness of 0.178 mm, with a photothermographic imaging layer and
a protective overcoat. The layers of the thermally processable
imaging element were coated on a support using an extrusion coating
hopper. The photothermographic imaging composition was coated from
aqueous solution at a wet coverage of 97.8 g/m2 to form an imaging
layer of the following dry composition
TABLE 1 Photothermographic Imaging Layer dry coverage Dry Coverage
Components (g/m.sup.2) Succinimide 0.761 4-methyl phthalic acid
0.109 Dev-1 1.935 Emulsion cubic edge 0.048 micron as silver 0.283
D-1 0.00391 D-2 0.00117 Silver behenate 7.652 Gelatin 5.435 Sodium
Iodide, USP 0.055 AF-1 0.0196 AF-2 0.0543
The resulting imaging layer was then overcoated with mixture of
polyvinyl alcohol and hydrolyzed tetraethyl orthosilicate as
described in Table 2 at a wet coverage of 40.4 cc/m.sup.2 and dry
coverage shown in Table 3.
TABLE 2 Overcoat Solution Component Grams Distilled Water 1158.85
grams Polyvinyl Alcohol (PVA, Elvanol .RTM. 52-22 763.43 from
DuPont, 86-89% hydrolyzed) (6.2% by weight in distilled water)
Tetraethyl Orthosilicate solution 489.6 comprising of 178.5 grams
of water 1.363 grams of p-Toluene Sulfonic Acid, 199.816 grams of
Methanol, 207.808 grams of Tetraethyl Orthosilicate Aerosol .RTM.
OT (0.15% by weight in distilled 75.00 water. (Aereosol OT is a
sodium bis-2- ethylhexyl sulfosuccinate surfactant and is available
from the Cytec Industries, Inc.., U.S.A.) Zonyl .RTM. FSN (0.05% by
weight in distilled 3.13 water. (Zonyl FSN surfactant is a mixture
of fluoro-alkyl poly(ethyleneoxide) alcohols and is a trademark of
and available from the Dupont Corp., U.S.A.) Silica (1.5 micron)
3.0
TABLE 3 Overcoat layer dry coverage PSA (Silicate) 1.302 PVA 0.872
Aerosol .RTM. OT 0.0624 Zonyl .RTM. FSN 0.0207
Structures of Components in Example 2. ##STR5##
The coating of Example 2 was exposed using the 810 nm, 50 mW, diode
laser sensitometer and heat processed at 122.degree. C. for 15 sec
to produce a developed silver image density Dmax=3.59 and
Dmin=0.065, see Table 4.
Control Example 3
Procedure for Precipitation of Silver-Behenate, Phthalazine-Free,
Nanoparticulate Colloidal Dispersion
A nanoparticulate, phthalazine-free, silver-behenate colloidal
dispersion was prepared as described in Example 1 except
phthalazine toner was not included in the reaction mixture during
the precipitation.
Control Example 4
IR Sensitive Aqueous Photothermographic Imaging Element Formulated
Using Phthalazine-Free AgBeh Dispersion
A photothermographic element was formulated, coated, exposed and
heat processed as described in Example 2 except that the silver
(behenate-silver phthalazine toner) compound combination
nanoparticulate dispersion of Example 1 was replaced with the
phthalazine-free nanoparticulate AgBeh dispersion of Example 3.
The imaging element was exposed and processed as described in
Example 2 to produce a developed silver image having sensitometric
characteristics as shown in Table 4.
The maximum density for the element of the invention is much higher
than for an element having "free" toner.
Examples 5-16
Photothermographic elements were formulated using silver source
dispersions and silver halide coverages listed in Table 4a, and
coated, as described in Example 2.
The imaging elements were exposed and heat processed as described
in Example 2 to produce a developed silver image having
sensitometric characteristics as shown in Table 4.
Examples 17-20
Photothermographic elements were formulated using silver source
dispersions and silver halide coverages described in Control
Example 6, and coated, as described in Example 2.
The exposed imaging elements were exposed and heat processed as
described in Example 2 to produce sensitometric response as shown
in Table 4b.
Preparation of Silver-Phthalazine 1:1 Dispersion for Use in Control
Examples 17 and 18
A silver-phthalazine dispersion (1:1 molar ratio) was prepared by
first dissolving 1.96 g phthalazine and 0.78 g of 35% gelatin
solution (cattle bone, alkali treated, deionized gelatin) in 37.2 g
demineralized water. This solution was stirred vigorously at room
temperature while adding 4.70 g of 5.72 M AgNO3 solution.
Control Example 17
The silver-phthalazine dispersion (1:1 molar ratio) prepared above
was introduced into photothermographic imaging elements similar to
Example 4 at a level equivalent to 0.0435 g/m2 phthalazine.
Control Example 18
The silver-phthalazine dispersion (1:1 molar ratio) prepared above
was introduced into photothermographic imaging elements similar to
Control Example 4 at a level equivalent to 0.087 g/m2
phthalazine.
Preparation of Silver-Phthalazine 1:2 Dispersion for Use in Control
Examples 19 and 20
A silver-phthalazine (1:2 molar ratio) dispersion was prepared by
adding a solution of 0.333 g AgNO3 and 0.61 g gelatin (cattle bone,
alkali treated, deionized gelatin) in 5.14 g water into a
40.degree. C. stirred solution prepared from 0.5 g phthalazine, 1.0
g gelatin (cattle bone, alkali treated, deionized gelatin) and 8.5
g of demineralized water.
Control Example 19
The silver-phthalazine (1:2 molar ratio) dispersion prepared above
was introduced into photothermographic imaging elements similar to
Example 4 at a level equivalent to 0.0323 g/m2 phthalazine.
Control Example 20
The silver-phthalazine (1:2 molar ratio) dispersion prepared above
was introduced into photothermographic imaging elements similar to
Example 4 at a level equivalent to 0.0646 g/m2 phthalazine.
Control Example 21
This control example was prepared similarly to that of Example 2
except that the Nanoparticulate AgBeh used was free of phthalazine
and the amount of sodium iodide was reduced to 0.011 g/m.sup.2.
Example 22
Aqueous Photothermographic Imaging Element Formulated Using
Nanoparticulate Ag(Beh-Phtahlazine) Dispersion and Nanoparticulate
AgBeh.
Preparation of Dispersion Ph1
A mixture of 2.5 g dodecylthiopolyacrylamide, 0.65 g phthalazine,
1.88 g behenic acid, 215 g distilled water, and 5.0 ml of 1 M NaOH
were heated at .about.90.degree. C. until all components had
dissolved. The resulting solution was stirred at 80.degree. C.
while 48.3 g of 0.10M AgNO.sub.3 solution was rapidly added
requiring .about.2 sec. The mixture was rapidly cooled to
14.degree. C.
Examination of the resulting dispersion by electron microscopy
showed an average particle size of 50 nanometers. X-ray powder
diffraction spectrum of this sample showed that the predominate
peaks were those of AgBeh.
Example 22
Coating
This example coating was prepared similarly to that of Control
Example 21 except that 34.0 g of Dispersion Ph1 was added in
addition to the phthalazine free AgBeh. The resulting coating
contained 0.29 wt % phthalazine relative to the total weight of
AgBeh and 0.13 wt % phthalazine relative to the total weight of the
emulsion layer.
The coatings of Control Example 21 and Example 22 were exposed and
processed as described in Example 2. The sensitimetric results are
given in Table 4b. The resulting image of Example 22 had a more
neutral image tone (more desirable), higher Dmax, and greater speed
than that of Control Example 21.
TABLE 4a Silver (Behenate - Phthalazine Phthalazine (Free or Ag
Exam- AgBr Silver Toner) Salt) ple as Ag Source g/m2 of g/m2 of #
Example g/m2 Dispersion Phthalazine Phthalazine 2 Invention 0.283
Ag (Beh-Ph) 0.348 0 4 Comparative 0.283 AgBeh 0 0 5 Invention 0.175
Ag (Beh-Ph) 0.348 0 6 Comparative 0.175 AgBeh 0 0 7 Comparative
0.283 AgBeh 0 0.174 8 Invention 0.175 Ag (Beh-Ph) 0.696 0 9
Comparative 0.175 AgBeh 0 0 10 Invention 0.283 Ag (Beh-Ph) 0.174 0
11 Comparative 0.283 AgBeh 0 0 12 Comparative 0.283 AgBeh 0 0 13
Comparative 0.283 AgBeh 0 0.00087 14 Comparative 0.283 AgBeh 0
0.00174 15 Comparative 0.283 AgBeh 0 0.00870 16 Comparative 0.283
AgBeh 0 0.01739 17 Comparative 0.283 AgBeh 0 0.0435 18 Comparative
0.283 AgBeh 0 0.0870 19 Comparative 0.283 AgBeh 0 0.0323 20
Comparative 0.283 AgBeh 0 0.0646 21 Comparative 0.283 AgBeh 0 0 22
Comparative 0.283 AgBeh + Ag 0.022 0 (Beh-Ph)
TABLE 4b # Example Dmin Dmax Speed @ 1* Speed @ 2** 2 Invention
0.07 3.59 1.52 1.32 4 Comparative 0.07 2.80 1.50 1.30 5 Invention
0.09 2.82 1.39 1.15 6 Comparative 0.09 1.88 1.40 1.00 7 Comparative
1.49 1.49 no image no image 8 Invention 0.05 2.95 1.30 1.05 9
Comparative 0.06 1.52 1.20 1.00 10 Invention 0.07 3.10 1.37 1.22 11
Comparative 0.06 2.74 1.42 1.23 12 Comparative 0.07 2.84 1.39 1.19
13 Comparative 0.07 2.80 1.40 1.17 14 Comparative 0.07 2.55 1.32
1.09 15 Comparative 0.07 2.23 1.08 0.74 16 Comparative 0.07 2.39
1.00 0.76 17 Comparative 0.18 no image no image no image 18
Comparative 0.11 no image no image no image 19 Comparative 0.10 no
image no image no image 20 Comparative 0.12 no image no image no
image 21 Comparative 0.07 2.57 1.43 1.19 22 Invention 0.16 3.36
1.68 1.51 *Relative speed at 1.0 density in LogE **Relative speed
at 2.0 density in LogE
* * * * *